But Mr Jones told the chamber: "This is a commercial matter, primarily between the farmer involved and the supplier and that should be the first port of call."

Welsh Assembly Tory leader Nick Bourne later told the chamber: "I hope the minister will not close the door on the possibility of some form of compensation contribution."

Mr Jones said the infected seed potatoes were detected during an annual EC survey for ring rot, which is carried out by the Plant Health and Seeds Inspectorate.

The movement of all potentially contaminated stock has been halted.

Mr Jones said three farms in the south west of England that have been confirmed as having received seed potatoes from Bwlch have been placed under restrictions. He said the seed in those locations has not been planted.

Brynle Williams, the Conservative agriculture spokesman, said he had been told by the Agricultural Development Advisory Service that the disease could cost the industry around &#xA3;10.7m.

He claimed: "If adequate preventative bio-security measures were taken, this would have cost around &#xA3;200,000, a saving of many millions of pounds and immeasurable distress to farmers."